Amphibious Cruiser

[Willallison]

I was pottering up a little river in my dinghy the other day. This would be a lovely place to live - boat parked out the front. Problem is, this river has a shallow entrance at a beach that at times is sompletely closed over.
Still as a bit of fun, I've started thinking about the sort of amphibious stuff that's about that would be adaptable to a planing power cruiser. I looked at the Sealegs RIB made in NZ, but can't imagine such a system working on aboat displacing around 6 tons - particularly as it has to cross sand.
There doesn't seem to be much else about.
Any ideas?

[joz]

Will

what about the S&S DUKW's of WWII vintage would that suit?

[kach22i]

Hovercraft.

I suggest a four stroke with a large slow and quiet propeller if you can get it. The two strokes with fans are not the best cruisers.


The Australian Hovercraft Federation Inc.
http://www.aushover.tk/

They make them down there too:

http://www.airlifthovercraft.com/

http://members.optusnet.com.au/%7Enell/

http://www.mariah.com.au/

Hovercraft love shallow rivers and sandbars.

I've always liked the Mustang by Airlift.



EDIT:
A personal site featuring a Mustang.

http://www.machineage.info/

[Willallison]

Nope - the 'ducks' aren't really what I was thinking of (too slow, thristy and cumbersome). Nor the hovercraft - at least not in the traditional sense. I'm trying to come up with a means of transporting an otherwise regular planing powerboat - about 40ft, 6 tons - over a stretch of sand maybe 50 - 100 ft across. The rest of the time it must operate efficiently as a regular cruising boat.
I had considered the idea of some sort of self propelled cradle, which could then be left moored off the beach whilst the boat is in use. However, the beach in question is relatively open to the ocean, so leaving anything moored there would be a bit of a gamble. Further, I have no doubt that local authorities would just laugh if you suggested putting a permanent mooring in.

[kach22i]

You may be looking at a hovercraft platform (barge), one with a hoist or powerful winch.

http://www.hovertrans.com/

[tom kane]

Go the simple way,a couple of pontoons each side of an ordinary hull that are fitted on cranks that rotate and take the hull forward and sit on the keel at the bottom of each revolution,hydraulic motor operated powerful and plenty of surface area,and each pontoon works independent to make sharp turns.And of course it has been done before.Pontoons can be adjusted when planing to lift the hull for less drag.

[kach22i]

Originally Posted by tom kane

And of course it has been done before.

Do you have any website links or photos?

Sounds very interesting.

Can you move a dock this way too?

[tom kane]

I have only seen the system shown in the 1960`s in some magazines and recently on a news item, also wheels were used in conjunction with the pontoons in some cases.You just have to see how tracked back-hoe-diggers operate and the loads they can move with their hydralics.It is not a fast moving vehicle but massive power and good surface area to go through soft surfaces.I tried the basic idea on a small aliminum hull to launch a boat through deep mud to reach the water on a droping tide,but using chains instead of hydraulics,to turn the cranks, as wheels were useless.

[safewalrus]

If the old 'James Bond' movies are anything to go by just steam at the bank full thottle and you'll crash over (might wipe your stern gear off the bottom of th boat but who's counting?)

[safewalrus]

But seriously the hover barge seems a bit OTT; I like your cradle idea though! How's about come in from sea, slide into cradle, lock the boat in position over the bank and then motor to the dock with cradle still attached! You then have fenders and a docking cradle in one - powering it could be tricky but some sort of power take off from the main boat engine shouldn't be too hard to organise?

When you run back to the beach launch into deep (?) water drop the cradle and either bouy off or pull it back onto the beach for your return! OK so fitting into and dropping the cradle could be cumbersome but not to much! Shouldn't be too expensive either - then you can spend the money were best appreciated - on the boat!

[Willallison]

Tom - very interesting concept. Given that speed is of no consequence, it certainly bears further investigation - thanks

Wlarus - yes that's exactly the senario I envisage. Though to further complicate matters, there's a quite low bridge to get under once in the river, and draft is quite restricted.
Personally, I like the James Bond approach the best - but the local bathers might object to having to scatter as boat blasts its way across the sand at 30 knots!

[safewalrus]

Will - that's typical of bathers just no soul! I mean they should be Honoured to get out of the way! Still you can't please everybody eh! (Oh yes and if they don't get outa the way I guess a 'Viking launch' over the bodies of a few slaves may upset the local constabulary!)

[alexlebrit]

There's always a

[yipster]

or build 2 dykes and locks

like to see james bond do it on a 6 ton giant catarpillar snowscooter tho

[safewalrus]

Looks like the good old Sewage Canal to me, Mr Bond went thro' there in the late fifties early sixties (can't remember when - but he had a little help from other Naval and Marine (Royal) Commandos and a few Para's............easy!!